The present invention relates to an apparatus for measuring parallel light rays and a measurement of the parallelism of light rays used for a sensor to which optics has applied.
There has been a wide use of optical sensors adopting various lasers. LEDs or the like as light sources. Many of these sensors employ parallel light rays as a part of the optical system. A parallel light ray can be formed of the combination of a light emitting section and a collimator lens in the case where the emitter is nearly a point such as an LED, laser diode and the like; alternatively, a parallel light ray can be formed of the combination of a light emitting section and a beam expander in the case of a He-Ne laser and the like. The quality of the parallel light ray, more specifically, the extent to which the light ray in the parallel light flux is parallelized has much effect on the performance of the sensor itself; as a result, the parallelism of a light ray is determined depending upon not only the performance of each optical device but also upon the relative positional accuracy between those optical devices. Accordingly, arranging each of optical devices needs a measuring apparatus for measuring the parallelism of a light ray with precision, and an adjusting apparatus for precisely shifting relative positions between each optical device and the devices.
The measurement of parallelism of a light ray by the conventional method has been carried out by measuring the distortion of the wave front of the light ray by means of an interferometer, and also performed in accordance with a noncoherent lamp or the light of an LED, by measuring and comparing the sizes of the light beam or light intensity distribution between in the close site and in the distant site, or by following up the the light ray using a pin hole.
The interferometer mentioned above for measuring the distortion of the wave front of the light ray is structurally complicated, and the processing of the obtained interference fringes is not a simple one. Furthermore, it has been difficult to perform a measurement when a laser ray which has a rather poor coherence is used since it exhibits poor contrast of the interference fringes. On the other hand, in the case where the size of the light ray and the light intensity distribution are measured, it is difficult to measure an exact contour; or the measurement takes much time, consequently, the conventional interferometer has exhibited a poor effectiveness.